I've had grooved/drilled disks on my MX5 before now with no problems, 'But' I'm not the fastest driver in the world, (It was my track car not just an everyday hack)
I'd be happy to use them again on a road car, but you can get the dimpled ones which IMHO don;t look as good or offer the cooling of fully drilled but they might do you?
When I finally get round to swapping my disks/pads (If I can ever reach a point where breakdowns stop taking all my disposable income) then I'll go for grooved/fully drilled with EBC red/green stuff pads (I don;t know how good this will be as I have'nt tried anything other than stock on my Alfa, but I had good results on my (much lighter) MX5, Like I said I'm not the fastest driver, these just suited my ability)
With anything other than a stock disk/pad arrangement I would expect the inspection intervals to be short enough to find any problems early enough to fix (just as you did with your cracked disks Rob (If you hadn;t been adjusting the toein you would have propbably found another reason to be under the car and have a quick look anyway?))
I've tried, plain vented, drilled, grooved, grooved and drilled, dimpled... The EBC dimpled discs were a bit of a dissapointment to be honest. I thought they would offer the benefits of drilled discs without the problems with cracking but they just didn't seem that great. For high performance, I'd stick with grooved discs but for plain road use, plain discs are fine to be honest. Pad wear is higher with grooved discs.
Incidentally, the cross-drilling does not significantly aid cooling as I understand it. Instead the primary benefit is that it allows gasses to escape from between the pad and disc plus builds up pad material on the leading edges of the holes to improve bite.
For pads, again I've tried EBC Green, EBC Red, Ferrodo DS2500 and Pagid. The best pads depends entirely on the car so I don't have any experience on the Alfa yet. I'd say that the Ferrodo and Pagid pads are better than the EBC variants from my experience on a much lighter car. The pads bring a greater difference than the discs.
For brake feel, the best mod I ever did (again non-Alfa) was to replace the old rubber hoses with BF Goodridge braided hoses.
Interesting info here: http://www.apracing.com/products/rac...ake_discs.aspx
For my 159 for road use, I will probably stick with plain discs and some uprated pads.
Testing sites include the Nurburgring, La Sarthe (Le Mans), Cadwell Park and the M6 Toll Road.
Oh one final thing. The best way of improving braking performance is to have a lighter car. I often wonder how good the 159 would be with a stripped out interior and some lightweight seats. My wife is not convinced!